The present invention relates, in general, to a control mechanism for vehicle parking brakes and, more particularly, to a control mechanism having a self-adjusting arrangement for automatically taking up slack in the brake cable and maintaining a predetermined minimum amount of tension therein.
Various types of both manually operated and foot operated mechanisms or devices have been developed and utilized for actuating and controlling the parking or emergency brakes of automotive vehicles. Such parking brake control mechanisms have generally included a fulcrumed brake actuator member or lever in conjunction with a locking means or device for holding the actuator lever in brake setting positions, the locking means being releasable to permit release of the parking brakes by the conventional brake springs.
With such prior parking brake control mechanisms, it has been generally necessary to manually adjust the parking brake cable periodically in order to take-up the slack which normally develops in the cable after extended periods of brake usage. If such slack is permitted to accumulate in the brake cable, the parking brake could eventually become totally inoperative and so lead to an unsafe operating condition for the automobile.
As disclosed in U.S. Pat. No. 3,236,120, one commonly known form of such parking brake control mechanisms employs a torsion coil spring the turns of which surround and frictionally grip a drum coaxial with the brake actuator lever fulcrum to retain the lever in brake setting position. With such type brake control mechanisms, excessive brake cable "back-off" is encountered, that is, the movement of the brake actuating cable in a brake releasing direction which occurs during the period that the torsion spring wraps itself tightly onto and grips the drum. Thus, in such constructions the vehicle operator actuates a brake actuator member or lever to set the parking brakes, but the lost motion of the torsion coil spring in frictionally gripping the drum effects a partial release of the brakes because of cable "back-off" which, together with the slack which normally develops in the cable during extended usage of the parking brake, renders the construction unsafe for automotive use.